Power control supported dynamic channel assignment in cellular radio systems

Transmitter power control is an effective technique to reduce co-channel interference and increase system capacity for cellular radio networks. Dynamic channel assignment can also be used to improve spectrum efficiency and thus increases the system capacity. This paper investigates channel assignment algorithms which combine dynamic channel assignment with signal-to-interference ratio balanced power control and proposes a new algorithm. Simulation results show that this new scheme can greatly reduce the channel reassignment rate and still maintain satisfactory performance. It may thus be used as an effective channel assignment scheme in cellular mobile systems. © 1997 by John Wiley & Sons, Ltd.     

Fixed preference channel assignment for cellular telephone systems

We describe a method of channel assignment for cellular telephone systems (in which a limited number of rearrangements are allowed) that gives good performance, controls rearrangements, and is easy to analyze. The method is based on an initial coloring of the interference graph, and channels are assigned to a cell of the network according to a preference list that depends on this coloring. We give a construction for such preference lists and prove that this construction is optimal     

Integrated predictive power control and dynamic channel assignment in mobile radio systems

It is known that dynamic allocation of channels and power in a frequency/time-division multiple access system can improve performance and achieve higher capacity. Various algorithms have been separately proposed for dynamic channel assignment (DCA) and power control. Moreover, integrated dynamic channel and power allocation (DCPA) algorithms have already been proposed based on simple power control algorithms. In this paper, we propose a DCPA scheme based on a novel predictive power control algorithm. The minimum interference DCA algorithm is employed, while simple Kalman filters are designed to provide the predicted measurements of both the channel gains and the interference levels, which are then used to update the power levels. Local and global stability of the network are analyzed and extensive computer simulations are carried out to show the improvement in performance, under the dynamics of user arrivals and departures and user mobility. It is shown that call droppings and call blockings are decreased while, on average, fewer channel reassignments per call are required.     

A pilot-based dynamic channel assignment scheme for wireless access TDMA/FDMA systems

We propose a control architecture for implementing a dynamic channel assignment (DCA) algorithm which optimizes two-way channel quality in a TDMA portable radio system. Computer simulations are used to evaluate the performance of this DCA method. A common control frequency, which is frame-synchronized among base stations, provides (1) beacons for portables to locate base stations and obtain DCA information, (2) broadcast channels for system and alerting information, and (3) pilot signals to permit portables to evaluate downlink interference. This allows low-complexity radio ports and portables to mutually select channels to avoid interference and avoid creating excessive interference. Results from computer simulations demonstrate the good spectrum efficiency of this method and its potential for handling nonuniform traffic demand. This work is targeted toward understanding the implications to local exchange networks of wireless system alternatives that could provide access to those networks.A preliminary work with the same title was presented at the Second International Conference on Universal Personal Communications, October 12–15, 1993, Ottawa, Canada.     

A model for channel sharing in land mobile radio dispatch services

A modeling approach to the problem of channel sharing in land mobile radio dispatch services, which is based on real life traffic data, is presented. In order to apply the GI/G/1 queueing model, the first step consists in identifying a message arrival process for each user by means of observed available data. It is then shown how to use simple approximation formulas to evaluate the expected waiting time, when two or more independent users must share a common channel. GPSS simulations were performed to verify that the proposed approach is suitable to practical applications.     

Uplink channel assignment with balanced load for code division multiple access cellular systems

In a code division multiple access (CDMA) wireless communication system, each mobile handset must be power controlled such that the power received at the base station is roughly the same. Otherwise, the interferences between mobile handsets will degrade the performance and increase the error rate. When a mobile handset uses channels from the neighbouring cells, it will raise its power to meet the threshold of signal strength. This will also increase the interference in the home cell. Therefore, we do not want a mobile handset to use channels from other cells blindly. In this paper, we propose an uplink channel assignment method based on the directed retry concept for CDMA cellular systems. The purpose is to achieve load balancing between neighbouring cells and at the same time controlling the interference levels at the base stations such that it will not affect the performance. Furthermore, priorities are given to handoff calls when assigning channels. Copyright © 2002 John Wiley & Sons, Ltd.     

A compact dynamic channel assignment scheme based on Hopfield networks for cellular radio systems

In this paper, a new channel assignment strategy named compact dynamic channel assignment (CDCA) is proposed. The CDCA differs from other strategies by consistently keeping the system in the utmost optimal state, and thus the scheme allows to determine a call succeeding or failing by local information instead of that of the whole network. It employs Hopfield neural networks for optimization which avoids the complicated assessment of channel compactness and guarantees optimum solutions for every assignment. A scheme based on Hopfield neural network is considered before; however, unlike others, in this algorithm an energy function is derived in such a way that for a neuron, the more a channel is currently being allocated in other cells, the more excitation the neuron will acquire, so as to guarantee each cluster using channels as few as possible. Performance measures in terms of the blocking probability, convergence rate and convergence time are obtained to assess the viability of the proposed scheme. Results presented show that the approach significantly reduces stringent requirements of searching space and convergence time. The algorithm is simple and straightforward, hence the efficient algorithm makes the real‐time implementation of channel assignment based on neural network feasibility. Copyright © 2008 John Wiley & Sons, Ltd.     

Multibeam cellular communication systems with dynamic channel assignment across multiple sectors

In cellular communication systems, directional multibeam antennas at cell sites can be used to reduce cochannel interference, increase frequency reuse and improve system capacity. When combined with dynamic channel assignment (DCA), additional improvement is possible. We propose a multibeam scheme using dynamic channel assignment across multiple sectors. A cell is divided into several sectors, each of which is covered by several directional beams. Specific channels are allocated to each sector as in fixed channel assignment (FCA). A channel of a sector is dynamically assigned to a wireless user who communicates through one of the several beams of the sector. The assignment is made so that constraints on the allowable cochannel interference are satisfied. Limitations due to cochannel interference are analyzed. A tractable analytical model for the proposed scheme is developed using multidimensional birth–death processes. Theoretical traffic performance characteristics such as call blocking probability, forced termination probability, handoff activity, carried traffic and channel rearrangement rate are determined. With the proposed scheme, call blocking probability can be reduced significantly for a fixed offered traffic. Alternatively, system capacity can be increased while blocking probability is maintained below the required level. Smaller forced termination probability is obtainable in comparison with corresponding FCA schemes.     

Compact pattern based dynamic channel assignment for cellularmobile systems

A new compact pattern based dynamic channel assignment strategy called CP-based DCA is proposed. The strategy aims at dynamically keeping the cochannel cells of any channel to a compact pattern. A compact pattern of a channel is defined as the pattern with minimum average distance between cochannel cells. CP-based DCA consists of two phases: channel allocation and channel packing. Channel allocation is used to assign an optimal idle channel to a new call. Channel packing is responsible for the restoration of the compact patterns and is performed only when a compact channel is released. Simulation results indicate that the CP-based DCA always performs better than the borrowing with directional channel locking (BDCL) strategy. In the designed example, CP-based DCA is shown to have 2% more traffic-carrying capacity than that of the BDCL in case of uniform traffic, and 8% more traffic-carrying capacity in case of nonuniform traffic, both at a blocking rate of 0.02. Besides, the number of channels reassigned per released call in CP-based DCA is at most one and is, therefore, another advantage over BDCL     

Neural network-based dynamic channel assignment for cellular mobilecommunication systems

Conventional dynamic channel assignment schemes are both time-consuming and algorithmically complex. An alternative approach, based on cascaded multilayered feedforward neural networks, is proposed and examined on two cellular systems with different configurations. Simulation results showed that the blocking performance of our multistage neural network approach can match that of an example conventional scheme with less complexity and higher computational efficiency. The example scheme considered here is the ordered channel search, which can achieve a reasonably high spectral efficiency as compared to that of an ideal dynamic channel allocation algorithm. We conclude that our neural network approach is well-suited to the dynamic channel allocation problem of future cellular or microcellular systems with decentralized control     

Spare reservation and distributed release based multiple access for satellite multimedia services

In this letter, we propose an efficient multiple access scheme for multimedia services in satellite networks, retransmission announced reservation multiple access (RARMA), in which resources are reserved according to the occasional demands by using spare reservation request and are released later by using a distributed release scheme. We analyze the throughput of RARMA, and show that our proposed scheme has a good throughput-delay characteristic through computer simulation.     

Future broadband radio access systems for integrated services withflexible resource management

The current challenge in radio networks is to provide integrated broadband services to everybody. The realization of this goal is dependent on both the development of products for the mass market and the improvement of the systems that support these products. New cellular mobile, fixed terrestrial, and satellite systems are being developed to provide broadband integrated services. The users of these new systems will not need, or even want, to know which particular systems are used to access the requested services. The users may negotiate terms of delivery, such as data rate and quality of service, but the actual system of delivery should be transparent. In order to both achieve transparent service delivery and ensure efficient use of the radio frequency spectrum, a flexible and scaleable resource management system is needed. This article highlights the development trends that will form the basis of future network systems and presents some suggestions for the management and control of these systems     

Adaptive radio resource assignment for simultaneous services

An adaptive algorithm for selecting rate matching parameters has been developed to satisfy the operating frame error rate requirements for simultaneous services in 3G Universal Mobile Telecommunications System (UMTS) under Rayleigh fading channels. The results show that the adaptive algorithm can achieve the target error rates for multiplexed services of varying data rates and types, and only requires a few adjustments for convergence.     

Improved channel assignment scheme with access control for thecommon packet channel in WCDMA systems

We propose a channel assignment scheme with access control for obtaining better system performance within the common packet channel (CPCH) access procedure of wideband code-division multiple-access (WCDMA) systems. The proposed scheme is analyzed taking multiple access interference into consideration and is compared with other schemes in the 3rd Generation Partnership Project (3GPP): the basic scheme, the channel monitoring scheme, and the channel assignment scheme without access control. The results show that the proposed scheme provides high throughput, even under high-loading conditions, since the access control algorithm based on channel load prohibits excessive interference     

Hybrid access scheme based on one-phase preamble and channel monitoring/assignment for satellite communications

In this letter, we propose a hybrid access scheme for satellite communications, taking into account the long propagation delay. The proposed scheme uses the one-phase preamble of 3GPP2 for fast access and applies the channel monitoring/assignment scheme of 3GPP for more reliable transmission. The results of analysis and simulation show that the proposed scheme achieves high throughput and low delay according to propagation delays in satellite communication environments.     

Performance of autonomous dynamic channel assignment and powercontrol for TDMA/FDMA wireless access

We combine autonomous algorithms for dynamic channel assignment (DCA) and power control in a TDMA/FDMA wireless system as a medium access control (MAC) protocol. The DCA algorithm determines paired radio channels that experience the least interference and are least likely to cause interference. The power control algorithm uses local estimations of signal to interference ratio (SIR) at a receiver to iteratively command power adjustment on the desired transmitter. A common control frequency, which is frame-synchronized among base stations, provides all necessary information for DCA without blind slots. Computer simulations are used to evaluate system performance. Results from computer simulations demonstrate good spectrum efficiency and robustness. Although studied under a specific set of parameters, this type of MAC protocol can be applied in different wireless communications environments     

Capacity allocation and channel assignment in cellular radio systems using reuse partitioning

Reuse partitioning is a technique for providing more efficient spectrum reuse in cellular radio systems. A cell in such a system is divided into concentric zones, each associated with an overlaid cell plan. For these schemes an optimum channel assignment strategy is proposed. Numeric examples show capacity improvements of about 50% compared to conventional systems.<>     

蜂窝移动通信中一种分级紧致的动态信道分配方案

本文提出一种分级紧致的动态信道分配（CCDCA）方案。文中首先根据信道使用情况与业务量的关系，将小区分成“冷态”和“热态”，并给出了相应的阈值，然后在对“热态”的处理过程中利用“冷态”的先验信息，对不同状态的小区给出了不同的紧致措施。该方案还能保证小区间有较小的服务偏差，提高了整个系统的服务质量。文中还根据冷、热态的特点构造了一个二维马尔科夫链模型，计算出了模型的主要参数；其思想可用于分析多种信道分配问题。仿真结果证明CCDCA方案有较小的呼阻率和较高的频谱利用率。     

阴影衰落信道下多波束卫星移动通信系统的动态信道分配策略

针对已有动态信道分配策略在阴影衰落环境中性能损失较大的问题,对卫星移动通信系统的阴影衰落信道模型进行分析,提出了一种动态信道分配策略。该策略结合用户的运动状态,通过在用户的预测运动轨迹上选取抽样点,将这些抽样点的平均干扰作为信道分配的指标,并采用链路质量约束避免了流量较大时的性能恶化。仿真结果表明提出的动态信道策略可在不增大阻塞率的前提下,在中低流量时将用户平均信噪比提高约0.5 dB。该策略可以应用于阴影衰落信道下的地面移动卫星通信系统,以提高用户的平均链路性能。     

UMTS architecture for integrating terrestrial and satellite systems

This architecture proposal for the Universal Mobile Telecommunication System harmonizes several approaches to the evolving European Union mobile-systems standard. The architecture accommodates both satellite and terrestrial networks and allows a smooth transition from existing systems to UMTS